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Source: — Problem Solving |
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by shovan85 » Fri Oct 22, 2010 5:44 am
IMO C

Let O be the center.
arc ABC = 24 cm
The exterior angle substended by A and C at O is 120 + 120 = 240 (see the picture below)

Thus 240 deg --> 24 cm
Full circle 360 deg --> 36cm

So (pie)*(Diameter) = 36
=> Diameter = 36/(3.14) = 11.46
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by 5abi » Fri Oct 22, 2010 9:35 am
easier way if i may:

If the triangle is equalateral...that means each arc 1/3rd lengh is equal..total arc length for 2/3rds of the circumference is 24, so C = 36

C= 2piR we can have r = C/2pi -> 2R is the answer which is 11.4sh
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by shovan85 » Fri Oct 22, 2010 9:38 am
5abi wrote:easier way if i may:

If the triangle is equalateral...that means each arc 1/3rd lengh is equal..total arc length for 2/3rds of the circumference is 24, so C = 36

C= 2piR we can have r = C/2pi -> 2R is the answer which is 11.4sh
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by pzazz12 » Sat Oct 23, 2010 4:31 am
5abi wrote:easier way if i may:

If the triangle is equalateral...that means each arc 1/3rd lengh is equal..total arc length for 2/3rds of the circumference is 24, so C = 36

C= 2piR we can have r = C/2pi -> 2R is the answer which is 11.4sh

thank you very much......... for simple method...
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